Polyamides



Patented Oct. 17, .1939

PATENT OFFICE POLYAMIDES Ralph A. Jacobson, Wilmington, DeL,

E. I. du Pont de Nemours & Company,

assignor to Wilmington, Del., a corporation of Delaware,

Nb Drawing. Application August 12, 1936,

Serial No. 95,711

5 Claims.

This invention relates to polymeric materials and more particularly tonew polyamides.

As disclosed in application Serial Number 548,701, filed July 3, 1931,by W. H. Carothers now Patent No. 2,071,250 and in its continuingapplications Serial Numbers 180, and 181, filed January 2, 1935 nowPatent Nos.'2,071,253 and 2,130,523, and 74,811, filed April 16, 1936,highly polymerized polyamides of unusual properties may be derived frompolymerizable amino acids of the formula NHzGCOOH, and from the reactionof diamines whose amino nitrogens each carries at least one hydrogenatom, particularly those of the formula NH2G'NH2, with dicarboxylicacids of the formula HOOCG"COOH, in which G, G and G" are divalenthydrocarbon radicals. These polyamides are largely highmeltingcrystalline solids relatively insoluble in most organic solvents withthe exception of phenols and certain acids. These products can generallybe obtained in the form of superpolyamides, that is, products which canbe spun into useful fibers.

I have now found when the reactant or reactants of the above mentionedtype have a lateral substituent, as more fully described herein, thatproducts are obtained which have properties not possessed by thepolyamides heretofore known and which are adapted to new or additionaluses in the arts.

This invention has an object the preparation of new and useful polymericproducts. A still further object is the manufacture of products usefulin the textile, plastic, molding, coating, sizing, adhesive,impregnating, and related arts. Other objects will appear hereinafter.

As indicated above, the polyamides of the present invention are madefrom a polyamide-forming material or materials containing a lateralsubstituent. Thus the polyamide may be made by polymerizing an aminoacid such as Z-phenylmercapto-G-aminocaproic acid having the formula:

H substituent is hydroxyl The dibasic acid may contain the lateralsubstituent instead of or in addition to the diamine, a suitable dibasicacid being a-N dimethylaminopimelic acid having the formula:

nooccmcnlcnicmcncoon in which the lateral substituent is dimethylamino ICH3 It will be seen, then, that the lateral substituent or lateralfunctional group represents a nonamide-forminggroup other thanhydrocarbon, such as a group containing oxygen or sulfur (either aloneor in combination with hydrogen or a hydrocarbon residue) or nitrogenfree from replaceable hydrogen atoms which is attached to but which doesnot interrupt the chain of atoms separating the amide-forming groups.The chain of atoms separating the amide-forming groups may, however,contain atoms other than carbon. The products of the present inventionare therefore obtained from one or more reactants which provideinteracting amide-forming carboxyl and-amino groups, the amide-forminggroups in at least one of the reactants being separated by a chain of atleast two atoms to one of which is attached the lateral substituent. Thereactive amino groups contained in the compounds used in making my newpolyamides have at least one hydrogen atom attached to the nitrogenatom.

The objects of my invention are accomplished by heating to reactiontemperature, generally from to 300 C., n the presence or absence of asolvent or diluent, polyamide-forming reactants, at least one of whichcontains a lateral substituent, as defined above, in the chain of atomsseparating the amide-forming groups, until a polymeric product isobtained. The term polyamide-forming reactant is used to designate anycompound which, when heated alone or in admixture with a complementarypolyamideforming reactant, is capable of yielding a polyamide. Itincludes amino acids and its congeners (i. e., amide-forming derivativesof amino acids), diamines, and dicarboxylic acids and its congeners (i.e., amide-forming derivatives of dibasic carboxylic acids). Thus, incarrying out my invention, I heat to reaction temperature (preferably 5ISO-300 C.) either a polymerizable monoaminomonocarboxylic acid(including amide-forming derivatives thereof) containing a lateralsubstituent, or .substantially chemical equivalent amounts of a diamine(primary or secondary) and a dibasic acid or amide-forming derivative ofa dibasic carboxylic acid, at least one of which contains a lateralfunctional group, to reaction temperature until a polymer of the desiredproperties is formed. Reaction may also be carried out in the presenceof a solvent, a diluent which is a non-solvent for the polymer, or amixture of solvent and diluent. By amide-forming derivative of an acidis meant an ester, acid halide, amide, or anhydride. I prefer to reactdiamines and dibasic acids in making my new products. The reaction is acondensation polymerization involving the removal of the by-productwater, alcohol, phenol, hydrogen chloride, or ammonia, depending uponthe amide-forming derivative of the acid used. In general, the productsformed are linear condensation polymers, but in some cases furtherreaction (cross-linking) occurs through reaction of the lateralfunctional groups.

When the polyamide is prepared from a diamine and a dicarboxylic acid,the first reaction which occurs on bringing the reactants intosufliciently intimate contact is the formation of thediamine-dicarboxylic acid salt. It is often desirable to separate andpurify this salt prior to its conversion into the polyamide. The saltsare generally crystalline, are readily purified by crystallization in asuitable solvent, such as water or alcohol, and have definite meltingpoints. Analytical data indicate that these salts are derived from thereaction of one mol of diamine with one mol of dicarboxylic acid. Thepreparation of the salts affords an automatic means of adjusting theamine and acid reactants to substantial equivalency and avoids tendantupon the preservation of the isolated amines in the state of purity. Theformation and purification of the salts also tends to eliminateimpurities present in the original diamines and dibasic acids.

As already stated, the polyamides of this invention are made by heatingthe reactants at the temperatures required for amide formation. Theheating may be carried out in an open or closed reactor under ordinary,reduced, or increased pressure, Usually it is desirable to carry out thereaction under conditions which permit the removal of the water or otherby-product formed in the reaction. It is advantageous to carry out thereaction in the absence of air; the

addition of an antioxidant is sometimes desirable. Generally, it isunnecessary to add a catalyst; however, inorganic substances of alkalinereaction, such as oxides and carbonates, and acid substances, such ashalogen salts of polyvalent elements, e. g., aluminum, zinc, and tin,are sometimes helpful.

The following examples in which parts are given by weight illustrate thepreparation of typical products of this invention:

EXAMPLE I Polyamide from phoronic acid and decamethylenediamine Anethanol solution acid,

of 25 parts of phoronic the difiiculties atwas a light-yellow, clear,hard determined Films cast on glass from were clear, tough, and hadpenetrometrically.)

solutions of the resin ood adhesion.

Exams: II

Polyamide from ethyl acetonedicarbozylate and decamethylenediamineEighty-five parts of decamethylenediamine and parts of the diethyl esterof acetonedlcarboxylic acid, CzHsOOCCHzCOCHzCOOCzI-Is, were heatedtogether as follows: C./760 mm., 20 minutes; 130-l90 C./'760 mm., 40minutes;

soluble in a mixture of approximately equal volumes of ethanol andbenzene. The resulting polyamide was a tough, horn-like, amber-coloredresin. It had a softening point of about 30 C.

Exmnn III Polyamide from adipic acid and 1,3-diaminopropanol-2 A mixtureof 29.2 parts of adipic acid and 18 parts of 1,3-diaminopropanol-2 washeated for 0.5 hour at 220C./760 mm. and then for 2.0 hours at 220C./90mm. The resulting polyamide resin, which was soluble in water, slightlysoluble in ethanol, and insoluble in benzene. It softened at about 65 C.

EXAMPLE IV Polyamide from methoxy dimer of methyl methacrylate andhezamethylenediamine A solution of 5.8 parts of hexamethylenediamine in40 parts of ethanol was heated with 11.6 parts of the methoxy dimer ofmethyl methacrylate for 1.0 hour up to 180 C., 1.5 hours at 180 C., 0.5hour at 180220 C., and finally for 1.0 hour at 220 C. The product was anambercolored syrup which was soluble in ethanol and in benzene. Themethoxy dimer of methyl methacrylate was prepared by the addition ofmethanol (using sodium methylate) to methyl methacrylate in the presenceof benzoyl peroxide. Although the exact structure of this compound isnot known, analytical data show that it is a dimethyl ester of adicarboxylic acid containing a methoxy (ether) group, possibly CH0OCCH(CH3) cntocm) cnzcmcm) COOCHa EXAMPLE V Polyamide fromthioglycollic acid, phorone, and decamethylenediamine Phorone (13.8parts) and thioglycollic acid (2 .3 parts) were mixed and allowed tostand about three weeks at room temperature, heated eight hours on thesteam bath, and finally heated under 2 mm. absolute pressure at- C. toremove any unreacted materials. The product (bis-thioglycollic acidether of phorone) was a syrup. It was formed by the addition ,of

probheavy two mols of the acid to one of phorone and ably has thestructure.

nooccmscwm)lcmcocmcwmhscmcoon Nineteen parts of this material was heatedwith 10.6 parts of decamethylenediamine for 1.5 hours at 215-220" 0. Theresulting polyamide wasa reddish-brown resin which was soluble in butylacetate, ethanol-benzene mixtures, and in the ethyl ether of ethyleneglycol, It ww plastic at room temperature, and was useful in coatin8compositions.

In the examples cited no added solvent or diluent was used. The reactioncan also be carried out in the presence of an inert solvent of whichmonohydric phenols, e. g., phenol, cresols, xylenols, and h'ydroxydiphenyls, are especially useful. Inert non-solvents such ashydrocarbons may be used. when easily volatile reactants are used, it isdesirable to carry out at least the initial stage of the reaction in aclosed vessel or under reflux to prevent loss of reactants. The productsof this invention are conveniently prepared in an open reactor equippedwith a reflux condenser which permits the water or other by-products ofthe reaction to escape but not the reactants or solvent. During thelatter stages of the reaction, it is often desirable to decrease thepressure in order to complete the reaction and, if desired, to distilloi! the solvent. However, the products can be removed from the solventby precipitation methods.

Examples I, II, and V illustrate polyamides derived from diamines anddicarboxylic acids or their amide-forming derivatives (estershcontaining oxygen (in form of carbonyl group) as the lateral functionalgroup. The acid (ester) used in Example V also contains the hetero-atom,sulfur in the chain. Examples III illustrates a polyamide derived from adicarboxyllc acid and a diamine containing the lateral functional group'hydroxyl, while Example IV discloses a polyamide containing a lateralfunctional group of the ether type;

In a similar manner the lateral substituents in the products may befurnished by other laterally substituted functional groups, e. g.,thioethentertiary amines, acetals, and thioacetal groups. As additionalexamples of dibasic acids (or amide-forming derivatives thereof)containing lateral functional groups may be mentioned tartaric acid,malic acid, mucic acid, ethoxy-succinic acid, diketosebacic acid, benrphenone dicarboxylic acid, and acids of the type nooccncmcnlcncoon mom),mom),

These acids or their amide-forming derivatives may be condensed withdiamines of which the following are illustrative: ethylenediamine,tetramethylenediamine, pentamethylenediamine, hexamethylenediamine,octamethyienediamine, decamethylenediamine, p-xylylenediamine, andbeta,beta' diaminodiethyl ether. The products of this invention can alsobe prepared by reacting diamines containing lateral functional groups,e. g., 1,3 -diaminopropanol-2, 1,3-diamino- 2-mercaptopropane, and1,2-diaminomethyl dioxane CH: 6H.

o with dibasic acids, such as carbonic, oxalic,

maleic, glutaric, adipic, beta-methyl adipic, pimelic, suberic, azelaic,sebacic, p-phenylene diacetic, diglycollic acid, and diphenylolpropanediacetic acid. As examples of amino acids containing laterallysubstituted groups which may be used in the preparation of the productsof this invention may be mentioned and 11 nnscnlcmcmecmcoon It will beseen from the above description that many combinations of reactants arepossible in the preparation of the polyamides of this invention. Furthercombinations are possible by reacting one or more diamines with one ormore dicarboxyllc acids, at least one of which contains a lateralfunctional group. Similarly, interpolymers can be prepared from thereaction of one or more monoaminomonocarboxylic acids withdiamine-dibasic acid mixtures in which at least one reactant contains alateral functional group. Moreover, it is within the scope of thisinvention to mix preformed polyamides at least one of which is derivedfrom a polyamide-forming reactant containing a lateral functional group.Products of this invention can also be mixed with other polymers, e. g.,with the fiber-forming poly-' mers described in the previously mentionedapplications. Thus, it is possible to add substantial amounts of apolyamide containing a lateral functional group to a superpolyamide, e.g., polyhexamethylene adipamide, and obtain a product whose propertiesclosely resemble that of the unmodified superpolyamide; the mixedpolymer can be spun from melt into filaments capable of being cold-drawninto oriented fibers.

The polyamides made according to the practice outlined above all containat least one lateral substituent which appears in the divalent, or-

' preparation of the polymer. If the polyamide is obtained exclusivelyfrom a polymerizable monoaminomonocarboxylic acid, NHzRCOOH, in which Ris a divalent organic-radical having a lateral substituent insertedalong the chain of carbon atoms separating the amino and carboxylgroups, then this substituent will be present in each recurring unit(-NHRCO) in the polyamide. If the polymer is derived from a mixture ofpolymerizable amino acids onlyone of which contains a lateralsubstituent, the said substituent will of course appear less frequentlyin the polymer molecule.

In the case of the polyamides made from diamines and dicarboxyllc acids,it will be apparent that several types of polyamides containing lateralfunctional groups can be prepared. For example, those in which thediamine (NHzR'NHz) represented contains a lateral substituent, those inwhich the dibasic acid (HOOCR"COOH) contains a lateral substituent, andthose in which both-the amine and acid contain a lateral substituent. Inthe formulae R. and R" represent divalent. organic radicals containing alateral substituent inserted along the chain of carbon atoms separatingthe amide-forming group, that is, the amino and carboxyl groups. Stillfurther combinations are possible by using diamines and dibasic acidsfree from lateral substituents along with diamines and/or dibasic acidscontaining lateral substituents. It is alsopossible to use polymerlzableamino acids in conjunction with a diamine and a dibasic acid, providingat least one of said reactants contains a lateral substituent. It isevident thereforethat at least one of the reactants used in thepreparation of the products of this invention has the formula XR"Y, inwhich X and Y represent amino or carboxyl groups and R' represents adivalent organic radical containing a lateral functional group in thechainof atoms separating'x and Y. On hydrolysis with strong mineralacids the products of this invention, except those of the heat hardeningtype, generally yield the reactants from which they were derived, theamino constituents being obtained inthe form of their mineral acidsalts.

The products of the present invention are for the most part resinous andunlike thepolymers described in the previously identified applicationsare soluble in a large number of common organic solvents and. aretherefore better adapted to the preparation of coating, impregnating,sizing, adhesive, and molding compositions than are the known polyamidesmade from reactants which do not contain a lateral substituent. The

products ofthis invention may also be used in the preparation of fibers,but for thispurpose it is generally desirable to prepare the products inthe presence of polyamide-forming reactants which yield superpolymers,or to incorporate these products with a fiber-forming ingredient, suchas a cellulose derivative or a fiber-forming polymer of the kinddescribed in the above men tioned application.

The softening temperature and solubility characteristics of the resinouspolyamldes described herein are dependent somewhat upon the reactantsfrom which they are prepared. In general, they are soluble in suchsolvents as' alcohols, esters, monoethers of ethylene glycol, dioxan,and alcohol-aromatic hydrocarbon mixtures. For the most part they havegood compatibility characteristics and can be mixed with drying oils,\iarious resins, cellulose derivatives, plasticizers; and otheringredients which are used in the preparation of coatings and plasticcompositions. Some of the products of this invention owing to thereactivity of the lateral substituent are of the heat-hardening type, i.e., they can be converted by heating into insoluble products.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

Iclaim:

1. A polyamide consisting of the reaction product of substantiallysolely bifunctional polyamide-forming reactants at least one of whichcontains a lateral substituent in the chain of atoms separating theamide-forming groups, said amide-forming groups being attached toaliphatic carbon atoms, and saidlateral substituent being one selectedfrom the'class consisting of ether and thioether groups.

2. A polyamide consisting =of the reaction product obtained byheating'as substantially the sole reactant a compound of the classconsisting of polymerlzable monoaminomonocarboxyllc acids of the formulaNHzRCOOI-I in which the amideforming groups are attachedto aliphaticcarbon atoms, and amide-forming derivatives thereof containingthecarbonyl group of the carboxyl group, in which R is a divalent organicradical having a chain ofatoms to which is attached a lateralsubstituent selected from the class consisting of ether and thioether,groups.

. 3. A polyamide consisting of the reaction product of reactantsconsisting substantially solely of a diamine of the formula NHaR'NHz inwhich the amino groups are attached to allphatic carbon class consistingof dibasic acids of the formula HOOCR' COOH, and amide-formingderivatives thereof containing the carbonyl group of the carboxyl group,wherein R and R" are divalent organic radicals at least one of which hasa chain of atoms to which is attached a lateral substituent selectedfrom the class consisting of ether and thioether groups.

4. A process which comprises heating to reaction temperature until apolymeric product is obtained reactants consisting substantially solelyof a compound of the class consisting of polymerizablemonoaminomonocarboxylic acids of the formula NHzRCOOH in which theamideforming groups are attached to aliphatic carbon atoms, andamide-forming derivatives thereof containing the carbonyl group of thecarboxyl group, where R is a divalent organic radical having a chain ofatoms to which is attached a lateral substituent selected from the classsisting of ether and thioether groups;

5. A process which comprises heating to reaction temperature until apolymeric product is obtained reactants consisting substantially solelyof a diamine of the formula NHzR'NHz in which the amino groups areattached to aliphatic carbon atoms and a compound of the classconsisting of dibasic acids of the formula HOOCR"COOH, and amide-formingderivatives thereof containing the carbonyl group of the carboxyl group,wherein R and R are divalent organic radicals at least one of which hasa chain of atoms to which is attached a lateral substituent selectedfrom the class consisting of etherand thioether groups. 1 i

RALPH A. JACOBSON.

atoms and a compound of the

